As the rumors of Chelsea's latest transfer triumph rustled around West London on Wednesday night, the events on the Stamford Bridge pitch spoke to one unavoidable truth about Rafa Benitez's star-studded squad. Without Mata, the Blues become bland.

As evidence, the shocker of the season. Queens Park Rangers, eight points adrift of safety and the league's worst team, defeated white-hot Chelsea on Wednesday at Stamford Bridge. With that, the Blues' four-match winning streak ended and the Rangers found reason to hope 2013 will provide the backdrop to yet another dramatic escape.

And yet, for want of a certain stylish Spanish playmaker, it might have been much different.

Not long after kickoff, Newcastle United manager Alan Pardew confirmed on Sky Sports TV that Senegalese will be heading to Chelsea "with our blessing" (via ESPN.co.uk). The official announcements will follow and Chelsea will have, at worst, another striker to provide depth and challenge the perennially underperformingFernando Torres for pitch time.

But while buying the Senegalese striker could—probably should—turn into a prudent piece of footballing business, the most important piece of the puzzle already roams the pitch in West London. Except that he didn't for the first 75 minutes Wednesday night.

Benitez benched Mata, along with fellow midfielder Eden Hazard, for the visit of the bottom-dwelling Queens Park Rangers. In a vacuum, it was probably a decent decision, with two cup ties looming in the next seven days.

In practice, though, it backfired.

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Chelsea labored, bereft of ideas, for more than an hour before Mata's introduction. QPR then scored, held on for a dozen minutes or so and completed the club's first win at Chelsea in 34 years.

The inquest—though it never really stops under an owner like Roman Abramovich—will begin anew, and Benitez will face warranted questioning over his curious squad selection. Not only did Mata and Hazard start on the bench, but erstwhile defender David Luiz moved to midfield alongside Frank Lampard.

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In truth, none of those decisions would have prompted an outcry on their own. Taken together, though, they leave little room to wonder why Chelsea failed to create enough of an offensive spark. Star players need rest, even in a squad as large as Chelsea's, but perhaps the downtime could have come after Mata and Hazard had presumably led a winning first-half charge.

And besides, it seems silly to argue that Mata needed rest when 34-year-old Frank Lampard made his second start in four days.

Benitez: "The last games, Mata and Hazard have been playing. We can't carry on with the same players every game' #cfc

Either option—to rest or to press on—presented a gamble, and for that reason Benitez should avoid unbridled condemnation. Yet the Spaniard must take at least a bit of the blame.

Until Mata entered the match in the 75th minute, victory looked improbable. Chelsea largely failed to trouble QPR in a dull first half and—besides a sustained spell of pressure early in the second half—did not create enough opportunities to win.

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Mata's introduction brought fresh ideas, and after QPR stole ahead, the Spaniard's bending ball found BranislavIvanovic for a header not long before full time. Ivanovic's header sailed high with QPR keeper Julio Cesar marooned, and with that, the Blues were beaten.

Poetically enough, the fatal blow came from the foot of Shaun Wright-Phillips, a former Chelsea man himself. The final pass came from Adel Taarabt, whose presence meant little to the Blues, except to point out that a team's best playmaker ought to always be on the pitch when possible.

That lesson won't sit well with Chelsea's fans, a group that before kickoff finally seemed to have eased off their banner-waving criticism of Benitez. Winning by eight goals at Aston Villa will do that, but losing at home to the league's worst team might just reignite the hostile fire.

Heading into Wednesday night, Chelsea had an opportunity to close the gap on the Manchester duo atop the Premier League table. Instead, the Blues lost and Mata sat the bench for 75 minutes.

As manager, Benitez must make difficult choices. This time, it's hard to argue he made the right one.